1. Field of the Invention
This invention relates to a driving circuit for toy car, and more particularly a drive circuit to control a driving motor based on a throttle open signal from a transmitter.
2. Description of the Prior Art
When the toy car is run by a remote control operation in a circuit, an operator should control a car speed of the toy car in response to a curved course and/or a straight course. When the car speed is controlled, a throttle open degree control lever of a transmitter is operated to change a revolution number of the driving motor mounted on the toy car. It is requested to change a pulse width of a pulse signal which drives the driving motor.
For example, when the car speed is lowered when the toy car curves, a pulse width PW of the pulse signal is lessened, as shown in FIG. 7(a) thereby lowering the revolution number of the driving motor. On the other hand, when the speed of the car is raised to run the straight course, its pulse width PW of the pulse signal, as shown in FIG. 7(b) is enlarged, to raise the revolution number of the driving motor time, a pulse frequency P(1/f frequency) of the pulse signal is not changed but kept constant.
To this end, each circuit on which the toy car runs, a course lay-out and size of a course vary, and construction of the toy car body varies.
For example, there are often opportunities to use the driving motor of wheels, at a low speed revolution, thereby raising a torque at a low speed revolution high, to be able to run the curve course forcibly.
In a straight course with less curves, there are often opportunities to use the driving motor of the wheels at high speed; it is required to smoothly rotate the motor to raise a revolution efficiency of the motor at high.
For this reason, when the toy car is run on a curved course, the pulse frequency P of the pulse signal to drive the driving motor is preset at high (see solid line g1 in FIG. 8) to raise torque at a low speed revolution (see solid line g1 in FIG. 9).
On the other hand, for relatively straight course with few curves for the car drive, the pulse frequency P of the pulse signal to drive the driving motor is preset low, prior to a run of the car (see dotted line g2 in FIG. 8 graph), to smoothly rotate the motor, to raise revolution efficiency (see dotted line g2 in FIG. 9 graph).
Thus, the driving circuit in the prior art is pre-changed at its pulse frequency to meet the course. When the car is run on the curved course, for example, it is difficult to attain high revolution efficiency with smooth revolution of the motor, on the straight course.
On the other hand, when the car is run on the straight course, it is difficult to raise the torque on the curved course.